Batty (adjective)

1. Crazy, eccentric, or eccentricity.
2. Mentally unstable or unwell.

Origin:

From middle english bate "mad, insane".

Examples:

1. He"s a bit batty, but he"s harmless.
2. Her batty ideas were not taken seriously.
3. The old man was known for his batty behavior.
4. The artist's batty style was unique and unusual.
5. The scientist's batty theories were not supported by the scientific community.